Allowance for Loan Losses - Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status (Details) - Consumer - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,259,367	$ 1,256,024
Percentage of Total	100.00%	100.00%
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 1,247,862	$ 1,242,559
Percentage of Total	99.10%	98.90%
Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 11,505	$ 13,465
Percentage of Total	0.90%	1.10%
Residential Mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 697,367	$ 701,982
Percentage of Total	100.00%	100.00%
Residential Mortgage | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 689,585	$ 692,064
Percentage of Total	98.90%	98.60%
Residential Mortgage | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 7,782	$ 9,918
Percentage of Total	1.10%	1.40%
Home Equity
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 487,806	$ 482,284
Percentage of Total	100.00%	100.00%
Home Equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 484,131	$ 478,845
Percentage of Total	99.20%	99.30%
Home Equity | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 3,675	$ 3,439
Percentage of Total	0.80%	0.70%
Installment and Other Consumer
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 69,644	$ 65,852
Percentage of Total	100.00%	100.00%
Installment and Other Consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 69,596	$ 65,744
Percentage of Total	99.90%	99.80%
Installment and Other Consumer | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 48	$ 108
Percentage of Total	0.10%	0.20%
Consumer Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,550	$ 5,906
Percentage of Total	100.00%	100.00%
Consumer Construction | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 4,550	$ 5,906
Percentage of Total	100.00%	100.00%
Consumer Construction | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivables, recorded investment	$ 0	$ 0
Percentage of Total	0.00%	0.00%